Support bls12 381 temporarilly #351

Job	Run time
Rustfmt	22s
Clippy lint checks	41s
Wasm-compatibility (wasm32-unknown-unknown)	1m 16s
Bench (default)	15m 19s
Test (default)	10m 6s
Bench (asm)	15m 54s
Test (bn256-table)	10m 6s
Test (derive_serde)	9m 55s
Bench (bn256-table)	16m 3s
Wasm-compatibility (wasm32-wasi)	1m 9s
Test (asm)	9m 42s
	1h 30m 33s

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